Differential pressure poppet valve



May 27, 1969 G. J. LIGHTFOOT DIFFERENTIAL PRESSURE POPPET VALVE Filed Nov. 17, 1966 I N VENTOR. GEORGE J. LIGHTFOOT 46% 5 /0440 ATTORNEY United States Patent US. Cl. 103-228 13 Claims The subject invention relates to an improved discharge valve in a reciprocating pump. More generally, the invention covers a fluid control system having improved valves, particularly adapted for pumping fluids in cryogenic atmospheres.

Reciprocating pumps commonly use poppet valves to control the passage of fluids out of a pumping chamber into a discharge reservoir while at the same time preventing fluid flow from the discharge reservoir into the pumping chamber. Conventionally, these valve poppets are loaded against the valve seats either by springs or by gravity. Gravity loaded poppets have the disadvantage of requiring vertical mounting to allow the poppet to rest against the seat by the force of gravity. In many instances, however, particularly in space vehicles and the like, this is impossible to guarantee, and gravitation systems may vary or not exist. Springs and spring followers, on the other hand, are complex and subject to excessive wear. When you consider that the pump piston, and consequently the poppet, may be reciprocating at a rate of 20 cycles per second, it is readily apparent that the springs and spring followers will have a relatively short life. One type of prior art valve using a spring-loaded poppet is described in US. Patent 2,837,898, which issued on June 10, 1958, to P. M. Ahlstrand.

The improved discharge valve of this invention operates in the same manner as prior art poppet valves, but employs neither gravity nor springs for its energy source. Accordingly, the valve of the subject invention may be used in any gravitational orientation, and has a life which is not limited by the life expectancy of a spring or spring follower.

The discharge valve of this invention is used in a pump having a piston movable in a normal back-and-forth cycle capable of forcing a fluid through a cylindrical passageway. The improved discharge valve, which fits within the passageway and is adapted to control the discharge of fluid into a reservoir, comprises the following elements: a pumping chamber having a seat at one end adapted to seat a discharge blocking member (sometimes termed a poppet); a discharge reservoir; a discharge blocking member movably mounted between the pumping chamber and the discharge reservoir, the seat and the discharge blocking member being so sized that when the member is seated, the flow of liquid through the discharge valve is blocked; and at least two ports coupling the chamber to the reservoir to enable the difference in pressure on the chamber side or piston side and the reservoir side of the discharge blocking member to seat the member during the one cycle of pump operation, i.e., when the piston is moving in a direction away from the blocking member. In this manner, fluid is prevented from flowing from the reservoir into the passageway during the backstroke. The elements are also sized so that the pressure difference, at least in part, also holds the discharge blocking member away from the seat during a substantial part of the forward stroke of the cycle when the piston is moving towards the chamber. Therefore, during the forward stroke, fluid can flow through the valve into the reservoir.

The discharge valve and the fluid control system of this invention will be better understood from the more detailed description which follows making reference to the drawings in which:

FIGS. 1 and 2 show cross sectional views of the pump and discharge valve of the subject invention, FIG. 1 showing the pump during the downstroke and FIG. 2 during the upstroke.

Referring to the drawing, pump 10 has an inlet valve 11 for admitting fluid into the pump. The term fluid is a generic term including liquids and gases, and the pump of the subject invention is applicable to either. The fluid may be compressible. A piston 12 moves back and forth in a normal cycle, actuated by a reciprocating engine or motor, not shown, forcing fluids through the cylinder or cylindrical passageway forming a pumping chamber 13, defined by wall 13a. When piston 12 abuts the left end of pumping chamber 13, the piston is at bottom dead center; when piston 12 is at the right end, it is at top dead center. Discharge valve 14 is adapted to control the discharge of the fluid from the pumping chamber 13 through an outlet port 15 into a reservoir, not shown.

Discharge valve 14 comprises a chamber 16 having a first seat 17 at one end adapted to seat a discharge member, such as ball 18. Although the preferred illustrated embodiment uses a spherical discharge member (ball 18), this geometry is not required. A conical, cubical, or a member of other geometrical configuration capable of fitting snugly into first seat 17 so as to block the flow of liquid through the opening 19 is satisfactory. Accordingly, the term discharge blocking member is used to define all geometrical designs of such elements. However, for future ease of reference in this specification, the more restricted term ball will be used for discharge blocking member 18.

Ball 18 is movably mounted in chamber 16. Ball 13 and seat 17 (which is located at one end of pumping chamber 13 or similarly at one end of chamber 16) are so sized that when the ball is seated in seat 17, as shown in FIG. 1, the entire flow of liquid through discharge valve 14 is blocked. Discharge valve 14 has a second seat 21 at the opposite end of chamber 16. The second seat 21 and ball 18 are so sized that when the ball is seated in second seat 21, the flow of liquid into a first port 22 from pumping chamber 13 around ball 18 is permitted, but the flow of liquid through a second port 23 from the pumping chamber 13 is blocked by ball 18. The cross-sectional area of first port 22 is smaller than that of second port 23. (See FIGURES 1 and 2).

First port 22 and second port 23 extend from chamber 20 through outlet port 15 into the reservoir and thereby are in communication with the reservoir and pumping chamber 13. The difference between the pressure on the piston or pumping chamber side and on the reservoir side of ball 18 holds the ball seated against first seat 17, as shown in FIG. 1, during the backstroke (downstroke in vertical pump) of the piston cycle when the piston is moving in the pumping chamber 13 in a direction away from chamber 16. Fluid is thereby prevented during that backstroke from flowing from the reservoir into chamber 16. Note that when ball 18 is in seat 17, fluid cannot flow through opening 19 from either the first port 22 or the second port 23. Moreover, the pressure difference between the piston side and the reservoir side of ball 18 also holds the ball away from first seat 17 during a substantial part of the upstroke when piston 12 is moving from bottom dead center to top dead center in a direction towards chamber 16, as shown in FIG. 2. Therefore, during that forward stroke (upstroke in horizontal pump), fluid is permitted to flow through valve 14, through first port 22 and outlet 15, into the reservoir not shown.

Preferably, first port 22 and second port 23 are parallel to Wall 13a of the cylindrical passageway 13. In the preferred illustrated embodiment, the first port 22 is located with respect to ball 18 so that first port 22 is open to fluid passage from chamber 13 when the ball is in the second seat 21 during the upstroke, as shown in FIG. 2, but closed to such fluid passage during the backstroke when the ball is in the first seat 17, as shown in FIG. 1. One way of achieving this function is to construct the second port 23 as a cylindrical passage, as shown in FIG. 2, of smaller diameter than ball 18 so that flow is blocked by ball 18 when the ball is in the second seat 21. Proper operation of the first port 22 is achieved by sizing it to permit fluid passage through the port around ball 18 when the ball is in the second seat 21, as shown in FIG. 2. Note that first port 22 is located laterally beyond the surface of ball 18, permitting fluid flow around ball 18 when the ball 18 is in the second seat 21. It should he understood that there may be a number of ports 22 and 23, but it is preferred that only a single port 23 be employed and that this port be located centrally or more particularly co-aXial with the pump axis.

The fluid control system using the novel discharge valve of this invention includes a cylindrical hollow piston 12 mounted in the cylindrical passageway or pumping chamber 13 defined by wall 13a so that piston can move in a normal back-and-forth cycle so as to force fluid from inlet port 11 through the pumping chamber, valve 14, and out into the reservoir. The fluid moves as shown by the arrows through port 24 into the hollow interior chamber 20 of piston 12. From the construction of the system as shown, it is apparent that fluid can move from inlet 11 through port 24 and on into the hollow chamber 20 of piston 12 irrespective of the position of the piston in the cylindrical passageway.

Piston 12 includes an inlet valve 25 located at the opposite end of the piston from port 24. Inlet valve 25 includes an inlet ball 26 capable of moving between two positions during the backstroke illustrated in FIG. 1, fluid will pass through the inlet valve 25 from the hollow interior chamber 20 of piston 12 into pumping chamber 13. When inlet ball 26 is in the second of the two positions during the forwardstroke shown in FIG. 2, against seat 27, passage of fluid through the inlet valve 25 is prevented. Ball 26 is held in the first of the two positions shown in FIG. 1 -by the pressure of the fluid in hollow interior chamber 20 against ball 26 during the backstroke of the piston cycle illustrated in FIG. 1 as the piston moves from top dead center to bottom dead center. Cage 27 holds ball 26 adjacent to piston 12 during the backstroke. However, cage 27 does not prevent fluid flow during the backstroke around ball 26 out of the hollow portion 20 of piston 12 and into pumping chamber 13.

During the forwardstroke of the piston cycle, from bottom dead center to top dead center, ball 26 is held against seat 27 by the pressure of the fluid within the pumping chamber 13. During that portion of the cycle, fluid is being forced by the combination of piston 12 and inlet ball 26 through opening 19, discharge valve 14, outlet 15, into the reservoir.

It should be understood that inlet ball 26 need not be spherical; it too may have other geometries, adapted to fit in seat 27, in the same manner as explained earlier in connection with discharge ball 18.

The complete operation of the pumping system of this invention during the backstroke and forwardstroke of the piston will now be explained referring to FIGS. 1 and 2. During the backstroke, as shown in FIG. 1, no fluid is flowing into inlet 11, nor coming out of outlet 15. After the downstroke commences, ball 26 is held against cage 27. The fluid within pumping chamber 13 and within the hollow portion 20 of piston 12 remains substantially still. The face of piston 12 moves behind a body of fluid in a direction towards bottom dead center through the still fluid. Fluid thus flows around ball'26 and into pumping chamber 13. At the end of the backstroke, pumping chamber 13 is substantially filled with fluid. Allduring the backstroke, discharge ball 18 is held tightly against .4 first seat 17 by the pressure differential between second port 23 and pumping chamber 13. The motion of piston 12 towards bottom dead center creates a slight vacuum or reduced pressure in pumping chamber 13. Accordingly, the pressure in chamber 13 is slightly less than the pressure in the second port 23. Ball 18 is held tightly against seat 17 as a result of this differential pressure. Accordingly, fluid is prevented from flowing from the reservoir back through outlet 15 and the first or second ports 22 or 23, into the pumping chamber 13. Similarly, inertia of the fluid pressure of the fluid flowing around inlet ball 26 holds inlet ball 26 against cage 27 during the backstroke.

The situation is reversed during the forwardstroke, as shown in FIG. 2. As soon as piston 12, controlled by a conventional reciprocating engine or motor not shown in the drawing, begins to move from bottom dead center towards top dead center, inlet ball 26 is forced against seat 27 by inertia of the pressure of the fluid in pumping chamber 13 against ball 27. Accordingly, the hollow portion 20 of piston 12 is sealed. As piston 12 and ball 26 move towards top dead center, a lowering of pressure occurs in chamber 29. This lower pressure along with other forces causes fluid to be sucked into inlet 11 and accordingly into the hollow portion 20 of piston 12. Moreover, the fluid in pumping chamber 13 is pushed by the action of piston 12 and ball 26 (pinned to seat 27) through the opening 19 at the end of the pumping chamber 13. The pressure of this onrushing fluid forces discharge ball 18 away from first seat 17 and into second seat 21. When ball 18 is in second seat 21, the second port 23 is sealed so that no fluid flows through the second port 23 out through outlet 15.

It should be apparent that it is intended in the embodiment shown that fluid does not flow through second port 23 either during the backstroke or during the forwardstroke. This port is merely to provide the necessary pressure on ball 18 to insure its seating in seat 17 during the backstroke. However, when ball 18 is in the second seat 21, fluid is forced by the piston through the first port 22 (called the exit port) and through outlet 15 into the reservoir. Thus, during the forwardstroke, the contents of the pumping chamber are pumped through the exit port 22 and outlet 15 into the reservoir.

Once the piston 12 reaches top dead center, it begins to return towards bottom dead center and the entire cycle is repeated.

From the above description, it is seen that discharge ball 18 is controlled almost entirely by the differential pressures between the pumping chamber 13 and the second port 23. No springs or other mechanical mechanisms are required to shift the ball from seat to seat at the proper times during the pumping cycle. Accordingly, a longer-life valve system is achieved. Furthermore, the pumping system of this invention may be utilized in any gravitational orientation since the action of discharge ball 18 is relatively insensitive to the forces of gravity.

The above specific structure is representative of only a preferred embodiment of the invention. Many modifications and improvements may be made by one skilled in the art without departing from the spirit of the invention, or from its true scope, as set forth in the claims which follow.

What is claimed is:

1. In a pump having a piston movable in a normal back-and-forth cycle of forcing a fluid through a cylindrical passageway which in part forms a pumping chamber, the improved discharge valve adapted to control the discharge of said fluid from said pumping chamber into a reservoir therefor, said discharge valve comprising:

a seat in the proximity of one end of said pumping chamber and adapted to seat a discharge blocking member;

a discharge blocking member movably mounted be tween the pumping chamber and reservoir, said seat and said member being so sized that when said member is seated therein, the flow of liquid through said discharge valve is substantially blocked; and

first and second ports, at least, coupling said chamber to said reservoir to enable the difference in pressure on the piston side and the reservoir side of said member to seat said member during the downstroke of said cycle when the piston is moving in said direction away from said member, whereby fluid is prevented from flowing from said reservoir into said passageway and to enable the pressure difference to hold said member away from said seat during a substantial part of the upstroke of said cycle when said piston is moving towards said member, where by fluid can flow through said first port into said reservoir, said second port being located centrally, and said first port being laterally spaced from said centrally located first port.

2. The improved valve of claim 1 further characterized by said discharge member being a spherical ball.

3. The improved valve of claim 1 further characterized by a second seat in opposed relationship to said first seat and adapted to seat discharge member, said second seat and said member being so sized that when said member is seated therein, the flow of liquid into said first port from said pumping chamber is permitted but the flow of liquid through said second port from said pumping chamber is at least partially blocked by said discharge member.

4. The improved valve of claim 1 further characterized by said first and second port being parallel to said passageway.

5. The improved valve of claim 3 further characterized by said first port being located with respect to said discharge member so that said first port is open to fluid passage when said discharge member is in said second seat and closed to fluid passage when said discharge member is in said first seat.

6. The improved valve of claim 4 further characterized by said discharge member being a ball, said second port being a cylindrical passage of smaller diameter than said ball and sized so as to be blocked by said ball when said ball is in said second seat, said second port providing the major control action for seating said discharge member in said first seat.

7. The improved valve of claim 6 further characterized by said first port sized to permit fluid passage therethrough around said ball when said ball is in said second seat.

8. The improved valve of claim 1 in which the second port is located co-axially to the pump axis and said passageway, and said first port is spaced laterally from said second port.

9. The improved valve of claim 1 in which said first port is of smaller cross-sectional area than said second port. v

10. A fluid control system comprising:

a means defining a cylindrical passageway including a pumping chamber;

a cylindrical, hollow piston mounted in said passageway movable in a normal back-and-forth cycle capable of forcing a fluid through said said pumping chamber;

an inlet port to said cylindrical passageway at one end thereof located to permit the passage of fluid into one end of said hollow piston irrespective of the position of said piston in said passageway;

an inlet valve in said piston located at the opposite end of said piston, said inlet valve including an inlet ball movably mounted within said inlet valve, said inlet ball being capable of moving between two positions, when said inlet ball is in a first of said positions fluid will pass through said inlet valve from said piston into said pumping chamber, and when said inlet ball is in a. second of said positions, passage of fluid through said inlet valve is prevented, said ball being held in said first position by fluid pressure against it during the forward portion of the piston cycle;

a discharge valve within said pumping chamber sized to control the discharge of said fluid into a reservoir therefor, said discharge valve including a pumping chamber having a seat at one end adapted to seat a discharge blocking member, a discharge blocking member movably mounted in said chamber, said seat and said member being so sized that when said ball is seated therein, the flow of liquid through said discharge valve is substantially blocked, and first and second ports coupling said chamber to said reservoir so that the difference between the pressure on the piston side and the reservoir side of said member seats said member during the downstroke of said cycle when the piston is moving in said passageway in a direction away from said chamber, 'whereby fluid is prevented from flowing from said reservoir into said passageway, and so that said pressure diflerence holds said member away from said seat during a substantial part of said upstroke of said cycle when said piston is moving towards said chamber, whereby fluid can flow through said first port into said reservoir, said second port being located centrally, and said first port being laterally spaced from said centrally located second port.

11. The fluid control system of claim 10 further characterized by said discharge member being a spherical ball.

12. The fluid control system of claim 10 in which said first port is of smaller cross-sectional area than said second port.

13. The fluid control system of claim 10 in which said second port is located co-axially to said passageway, and said first port is spaced laterally from said second port.

References Cited UNITED STATES PATENTS 411,261 9/1889 Scrankel 103-230 XR 1,605,830 11/1926 Garber et al. 103178 2,675,759 4/1954 Yarger 103-178 XR 2,891,571 6/1959 Sparks 137512.1

ROBERT M. WALKER, Primary Examiner.

U.S. Cl. X.R. 131-512.]; 107178 

1. IN A PUMP HAVING A PISTON MOVABLE IN A NORMAL BACK-AND-FORTH CYCLE OF FORCING A FLUID THROUGH A CYLINDIRCAL PASSAGEWAY WHICH IN PART FORMS A PUMPING CHAMBER, THE IMPROVED DISCHARGE VALVE ADAPTED TO CONTROL THE DISCHARGE OF SAID FLUID FROM SAID PUMPING CHAMBER INTO A RESERVOIR THEREFOR, SAID DISCHARGE VALVE COMPRISING: A SEAT IN THE PROXIMITY OF ONE END OF SAID PUMPING CHAMBER AND ADAPTED TO SEAT A DISCHARGE BLOCKING MEMBER; A DISCHARGE BLOCKING MEMBER MOVABLY MOUNTED BETWEEN THE PUMPING CHAMBER AND RESEVOIR, SAID SEAT AND SAID MEMBER BEING SO SIZED THAT WHEN SAID MEMBER IS SEATED THEREIN, THE FLOW OF LIQUID THROUGH SAID DISCHARGE VALVE IS SUBSTANTIALLY BLOCKED; AND FIRST AND SECOND PORTS, AT LEAST, COUPLING SAID CHAMBER TO SAID RESERVOIR TO ENABLE THE DIFFERENCE IN PRESSURE ON THE PISTON SIDE AND THE RESERVOIR SIDE OF SAID MEMBER TO SEAT SAID MEMBER DURING THE DOWNSTROKE OF SAID CYCLE WHEN THE PISTON IS MOVING IN SAID DIRECTION AWAY FROM SAID MEMBER, WHEREBY FLUID IS PREVENTED FROM FLOWING FROM SAID RESERVOIR INTO SAID PASSAGEWAY AND TO ENABLE THE PRESSURE DIFFERENCE TO HOLD SAID MEMBER AWAY FROM SAID SEAT DURING A SUBSTANTIAL PART OF THE UPSTROKE OF SAID CYLCE WHEN SAID PISTON IS MOVING TOWARDS SAID MEMBER, WHEREBY FLUID CAN FLOW THROUGH SAID FIRST PORT ITNO SAID RESERVOIR, SAID SECOND PORT BEING LOCATED CENTRALLY, AND SAID FIRST PORT BEING LATERALLY SPACED FROM SAID CENTRALLY LOCATED FIRST PORT. 